Process for fabricating metal bus lines for OLED lighting panels

ABSTRACT

Systems and methods for the design and fabrication of OLEDs, including high-performance large-area OLEDs, are provided. Variously described fabrication processes may be used to deposit and pattern bus lines with a smooth profile and a gradual sidewall transition. Such smooth profiles may, for example, reduce the probability of electrical shorting at the bus lines. Accordingly, in certain circumstances, an insulating layer may no longer be considered essential, and may be optionally avoided altogether. In cases where an insulating layer is not used, further enhancements in the emissive area and shelf life of the device may be achieved as well. According to aspects of the invention, bus lines such as those described herein may be deposited, and patterned, using vapor deposition such as vacuum thermal evaporation (VTE) through a shadow mask, and may avoid multiple photolithography steps. Other vapor deposition systems and methods may include, among others, sputter deposition, e-beam evaporation and chemical vapor deposition (CVD). A final profile of the bus line may substantially correspond to the profile as deposited.

FIELD OF THE INVENTION

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, The University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

The present invention relates to systems and processes for fabricatingOLED lighting panels, and particularly for forming metal bus lines asmay be used in large-area OLED lighting panels.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processable” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

In a typical bottom-emission OLED device, the anode material isconventionally a transparent conducting oxide (TCO), which generatespower losses and Joule heating due to its relatively high resistivityand thin film thickness. For example, sheet resistance is typically inthe range of 10-100 Ohm/square for a thickness range of 50-200 nm. Thisis in contrast to metal, which is often used for the reflective cathode.This can result in brightness non-uniformity, which becomes more evidentwhen scaling up to large-area light panels. In order to improveuniformity, highly-conductive metal bus lines may be deposited inelectrical contact with the TCO electrode to provide improved currentdistribution across the panel. Bus lines can help distribute currentmore evenly across the entire panel with very little power loss. Asimilar approach may be applied to top-emission OLED devices, where asemi-transparent cathode is required. In this instance, uniformity maybe improved by depositing highly conductive metal bus lines inelectrical contact with the cathode. In a transparent OLED device,highly conductive metal bus lines may be deposited in electrical contactwith both electrodes.

The conventional way to pattern metal bus lines is throughphotolithography followed by a lift-off process. Many publishedmaterials have taught that an insulating layer (such as SiO₂ or aphoto-resist) is required to cover the bus lines to prevent shorting.U.S. Patent Application Pub. No. US 2003/0006697 by Weaver disclosessuch a device including a first electrode, an insulating strip disposedover a portion of the first electrode, and a bus line disposed on top ofthe insulating strip, such that the bus line is electrically insulatedfrom the first electrode by the insulating strip. International PatentApplication Pub. No. WO 2010/038181 A1 by Schwab et al. (“Schwab”) alsodescribes an OLED device where bus (shunt) lines are applied to anelectrode. Schwab goes on to describe how passivation (electricalinsulation) at least partially and preferably totally covering the buslines is required to prevent electrical shorting to an opposingelectrode. In fact, it has become a standard practice in the industry touse an insulating layer (e.g., SiO₂, SiN, polyimide etc.) to cover thebus lines to prevent electrical shorts occurring between the bus linesand the opposing electrode.

However, introducing an insulating layer, or grid, such as thosedescribed in the foregoing publications, can reduce the emissive areasince the area covered by the insulating material is non-emissive. Inaddition, shelf life of the OLED may be reduced if moisture is stored inthe insulating layer. Finally, bus lines and the insulating layer aretypically patterned using photolithography, which is time-consuming andexpensive.

SUMMARY OF THE INVENTION

According to aspects of the invention, systems, and methods for thedesign and fabrication of OLEDs, including high-performance large-areaOLEDs, are provided. In embodiments, fabrication processes may be usedto deposit and pattern bus lines with a smooth profile and a gradualsidewall transition. Such smooth profiles and gradual sidewalltransitions have been found by the inventors to, for example, reduce theprobability of electrical shorting at the bus lines. Accordingly, incertain embodiments, an insulating layer may no longer be consideredessential, and may be optionally avoided altogether. In cases where aninsulating layer is not used, further enhancements in the emissive areaand shelf life of the device may be achieved as well. As discussedfurther herein, by depositing and patterning bus lines according to thedescribed methods, improvements in the luminance uniformity oflarge-area OLED light panels may also be achieved.

In embodiments, bus lines such as those described herein may bedeposited, and patterned, using vapor deposition such as vacuum thermalevaporation (VTE) through a shadow mask, which may simplify thefabrication process by eliminating, for example, multiplephotolithography steps. Other vapor deposition systems and methods mayinclude, among others, sputter deposition, e-beam evaporation andchemical vapor deposition (CVD).

According to first aspects of the invention, a method of manufacturing alight emitting panel with a plurality of bus lines may include forming afirst electrode layer and forming an organic layer stack over the firstelectrode layer. A second electrode layer may be formed over the organiclayer stack. Embodiments may include patterning a plurality of bus linesby vapor deposition through a shadow mask on at least one of the firstelectrode layer, the second electrode layer, or such other layers thatmay allow the bus lines to be electrically connected to the firstelectrode layer and/or the second electrode layer. In embodiments, theplurality of bus lines may be in electrical contact with at least one ofthe first electrode layer and the second electrode layer. For example,an electrical contact may be formed by depositing the bus lines on anelectrode layer and/or depositing an electrode layer on the bus lines.

In embodiments, the plurality of bus lines may be in electrical contactwith the first electrode layer and the first electrode layer may bedeposited before the plurality of bus lines. In embodiments, theplurality of bus lines may be in electrical contact with the firstelectrode layer and the plurality of bus lines may be deposited beforefirst electrode layer. In embodiments, the plurality of bus lines may bein electrical contact with the second electrode layer and the secondelectrode layer may be deposited before the plurality of bus lines. Inembodiments, the plurality of bus lines may be in electrical contactwith the second electrode layer and the plurality of bus lines may bedeposited before the second electrode layer. In embodiments, a first setof the plurality of bus lines may be in electrical contact with thefirst electrode layer and a second set of the plurality of bus lines maybe in electrical contact with the second electrode layer.

In embodiments, a final profile shape of the bus lines may substantiallycorrespond to a profile shape of the bus lines as deposited. Inembodiments, the patterning of the plurality of bus lines may include atleast one of vacuum thermal evaporation (VTE) deposition, sputterdeposition, e-beam evaporation and chemical vapor deposition (CVD). Forexample, the patterning of the plurality of bus lines may includedeposition by VTE through the shadow mask.

In embodiments, the patterning of the plurality of bus lines may includeat least one of (a) selecting a thickness of the shadow mask; (b)selecting a position of a material source with respect to the shadowmask; and (c) controlling the gap between the substrate and the shadowmask based on the desired final profile shape of the bus lines. Inembodiments, the thickness of the shadow mask may be in a range ofapproximately 20 microns to 500 microns. In embodiments, the anglebetween the line connecting source and center of the substrate and thenormal line of the substrate may be in a range of approximately 0° to20°.

In embodiments, the organic layer stack may be grown on the bus lineswithout an interceding insulator. In alternative embodiments, aninsulator may be formed between the organic layer stack and the buslines. The insulator may be formed between organic layer stack and thebus lines without breaking vacuum. The final profile of the insulatinglayer may correspond to the profile of the insulating layer as formed.

In embodiments, the forming of the first electrode layer, the patterningof the bus lines, the forming of the organic layer stack, and/or theforming of the second electrode layer may be performed without wetprocessing.

In embodiments, a slope angle of a sidewall of the bus line may be in arange of, for example, 0.01°-30°, the slope angle measured based on aline between two points on the bus line sidewall at 10% and 90%respectively of bus line thickness. In embodiments, the maximum absolutevalue of the second derivative of the sidewall profile of the bus linelayer with respect to distance along the substrate surface may be, forexample, <1.0. A root-mean-square (RMS) value of surface roughness ofthe bus line layer along the sidewall may be, for example, <30 nm.

In embodiments, an electrode layer may be formed before the bus linesare patterned. In other embodiments, the bus lines may be patternedbefore an electrode layer is formed. In embodiments, an anode may beformed between the organic stacks and a substrate. In embodiments, acathode may be formed between the organic stacks and a substrate. Inembodiments, an electrode layer may be formed on both sides of the buslines.

According to further aspects of the invention, a light emitting paneldevice may include a first electrode layer and a plurality of bus linespatterned by vapor deposition. In embodiments, the light emitting panelmay also include an organic layer stack over the first electrode layerand the bus lines, and a second electrode layer over the organic layerstack. In embodiments, the plurality of bus lines may include a finalprofile shape substantially as deposited.

In embodiments, the organic layer stack of the device may be on the buslines without an interceding insulator. In alternative embodiments, thedevice may include an insulator between the organic layer stack and thebus lines. The insulator may be formed between organic layer stack andthe bus lines without breaking vacuum. The final profile of theinsulating layer may correspond to the profile of the insulating layeras formed.

In embodiments, a slope angle of a sidewall of the bus line layer of thedevice may be in a range of 0.01°-30°. In embodiments, the maximumabsolute value of the second derivative of the sidewall profile of thebus line layer of the device with respect to distance along thesubstrate surface may be <1.0. In embodiments, a root-mean-square (RMS)of surface roughness of the bus line layer along the sidewall may be <30nm

According to further aspects of the invention, another light emittingpanel device may include a first electrode layer and a plurality of buslines, with an organic layer stack over the first electrode layer andthe bus lines. A second electrode layer may be included over the organiclayer stack. In embodiments, the plurality of bus lines may include afinal profile shape having sidewall angles in a range approximatelybetween 0.01°-30°. The organic layer stack may be, for example, on thebus lines without an interceding insulator. Embodiments may include aninsulator between the organic layer stack and the bus lines.

In embodiments, the sidewall angle may be measured based on a linebetween two points on the bus line slope at 10% and 90% respectively ofbus line thickness.

In embodiments, the final profile shape may have sidewall angles, forexample, in a range approximately between 0.01°-20°, or between0.01°-10°, or between 0.01°-1°.

In embodiments, the maximum absolute value of the second derivative ofthe sidewall of the bus line layer with respect to distance along thesubstrate surface may be <1.0, and/or an RMS surface roughness of thebus line layer along the sidewall may be <30 nm.

Additional features, advantages, and embodiments of the invention may beset forth or apparent from consideration of the following detaileddescription, drawings, and claims. Moreover, it is to be understood thatboth the foregoing summary of the invention and the following detaileddescription are exemplary and intended to provide further explanationwithout limiting the scope of the invention claimed. The detaileddescription and the specific examples, however, indicate only preferredembodiments of the invention. Various changes and modifications withinthe spirit and scope of the invention will become apparent to thoseskilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the detailed description serve to explain the principlesof the invention. No attempt is made to show structural details of theinvention in more detail than may be necessary for a fundamentalunderstanding of the invention and various ways in which it may bepracticed. In the drawings:

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows an exemplary large-area OLED light panel with metal buslines.

FIG. 4 shows an exemplary process for forming OLED devices according toaspects of the invention.

FIG. 5 shows an exemplary cross section illustration of a panelstructure, where organic materials of the OLED stack are disposeddirectly onto the bus lines and anode.

FIG. 6 shows further details of a bus line profile according to aspectsof the invention.

FIG. 7 shows a related art OLED device structure including passivation(insulating layer) on top of metal bus lines.

FIG. 8 shows a 3D AFM image of the slope of a bus line deposited by VTEthrough a shadow mask.

FIG. 9 shows data regarding the RMS of the VTE slope.

FIGS. 10A-10C show various aspects of changes in source location andmask thickness according to aspects of the invention.

FIG. 11 shows additional details regarding a source location accordingto aspects of the invention.

FIG. 12 shows SEM images of (a) top view and (b) side view 2600 Åaluminum bus line deposited by VTE through a shadow mask.

FIGS. 13A-13B show test results of a VTE deposited aluminum metal busline (Curve 2), and a second derivative of Curve 2, where a smoothtransition of about 0.06 is acquired.

FIG. 14 depicts an exemplary bus line pattern according to furtheraspects of the invention.

FIG. 15 includes SEM images of a tilted top view of 6000 Å metal busline profile patterned through lift-off process.

FIG. 16 is an SEM image of a side view of 6000 Å metal bus line profilepatterned through lift-off process.

FIG. 17 includes SEM images of a metal bus line profile patternedthrough lift-off process, where rough edge surfaces and defects can befound.

FIG. 18 is a cross sectional view of a device including an insulatinglayer covering the edge of bus lines.

FIG. 19 shows scanning electron microscope (SEM) images of (a) top viewand (b) side view of metal bus line profile fabricated from modifiedphotolithography process.

FIGS. 20A-20B show a profile of a metal bus line formed through amodified lift-off process (Curve 1) and a second derivative of Curve 1.

FIGS. 21A-21B show microscopic images of short spot on a bus line fromthe view of cathode side and anode side.

DETAILED DESCRIPTION

It is understood that the invention is not limited to the particularmethodology, protocols, and reagents, etc., described herein, as thesemay vary as the skilled artisan will recognize. It is also to beunderstood that the terminology used herein is used for the purpose ofdescribing particular embodiments only, and is not intended to limit thescope of the invention. It also is be noted that as used herein and inthe appended claims, the singular forms “a,” “an,” and “the” include theplural reference unless the context clearly dictates otherwise. Thus,for example, a reference to “a bus line” is a reference to one or morebus lines and equivalents thereof known to those skilled in the art.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art to which the invention pertains. The embodiments of theinvention and the various features and advantageous details thereof areexplained more fully with reference to the non-limiting embodiments andexamples that are described and/or illustrated in the accompanyingdrawings and detailed in the following description. It should be notedthat the features illustrated in the drawings are not necessarily drawnto scale, and features of one embodiment may be employed with otherembodiments as the skilled artisan would recognize, even if notexplicitly stated herein. Descriptions of well-known components andprocessing techniques may be omitted so as to not unnecessarily obscurethe embodiments of the invention. The examples used herein are intendedmerely to facilitate an understanding of ways in which the invention maybe practiced and to further enable those of skill in the art to practicethe embodiments of the invention. Accordingly, the examples andembodiments herein should not be construed as limiting the scope of theinvention, which is defined solely by the appended claims and applicablelaw. Moreover, it is noted that like reference numerals referencesimilar parts throughout the several views of the drawings.

The following preferred embodiments may be described in the context ofexemplary OLED devices for ease of description and understanding.However, the invention is not limited to the specifically describeddevices and methods, and may be adapted to various circuit assemblieswithout departing from the overall scope of the invention. For example,devices and related methods including concepts described herein may beused for the assembly of microchips, optoelectronic devices, such assolar cells and photodetectors, and other apparatus with multi-layercircuitry.

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, and a cathode 160. Cathode 160 is acompound cathode having a first conductive layer 162 and a secondconductive layer 164. Device 100 may be fabricated by depositing thelayers described, in order. The properties and functions of thesevarious layers, as well as example materials, are described in moredetail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporatedby reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. patent application Ser. No. 10/233,470, which is incorporated byreference in its entirety. Other suitable deposition methods includespin coating and other solution based processes. Solution basedprocesses are preferably carried out in nitrogen or an inert atmosphere.For the other layers, preferred methods include thermal evaporation.Preferred patterning methods include deposition through a mask, coldwelding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819,which are incorporated by reference in their entireties, and patterningassociated with some of the deposition methods such as ink jet and OVJD.Other methods may also be used. The materials to be deposited may bemodified to make them compatible with a particular deposition method.For example, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processability than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, televisions, billboards, lights forinterior or exterior illumination and/or signaling, heads up displays,fully transparent displays, flexible displays, laser printers,telephones, cell phones, personal digital assistants (PDAs), laptopcomputers, digital cameras, camcorders, viewfinders, micro-displays,vehicles, a large area wall, theater or stadium screen, or a sign.Various control mechanisms may be used to control devices fabricated inaccordance with the present invention, including passive matrix andactive matrix. Many of the devices are intended for use in a temperaturerange comfortable to humans, such as 18 degrees C. to 30 degrees C., andmore preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

As mentioned previously, the conventional method to form bus lines isphotolithography patterning, followed by a lift-off step. Aspects of thepresent invention, and comparisons to other known fabrication techniquesand devices are discussed further with respect to FIG. 3, which depictsa OLED panel 300, with emissive areas 310 and bus lines 320.

According to aspects of the invention an alternative means of depositingand patterning metal bus lines using, for example, vacuum thermalevaporation through a shadow mask has been developed. Such processeshave been shown to be, in general, simpler and less expensive thanphotolithography. Moreover, according to further aspects of theinvention, wet processes may be avoided, which can serve to reduce theamount of moisture that is retained in the device so as to extend thedevice shelf lifetime. As discussed further herein, the inventors havedemonstrated, for example, a large area OLED light panel with a devicelayer structure including a first electrode, bus lines, a secondelectrode and an emissive layer, in which the metal bus lines may bepatterned through VTE, and the like, followed by direct deposition ofthe organic layers. An increased emissive area can be achieved due tothe elimination of non-emissive insulating layer which is conventionallydeposited on to metal bus lines to prevent shorting. This can lead toincreased total light output for a given luminance, which in turnimproved device lifetime and efficiency.

For example, a process of manufacturing an OLED lighting panel includingbus lines, such as those generally depicted in FIG. 3, may include stepsshown in FIG. 4. The method may begin with S400 in which a firstelectrode may be deposited. The first electrode may be an anode. Inother embodiments, the first electrode may be a cathode. In embodiments,the first electrode may be deposited through a first shadow mask. Themethod may continue with S410.

In S410, a plurality of bus lines may be patterned by vapor depositionthrough a second shadow mask. In embodiments, the patterning of theplurality of bus lines may include at least one of vacuum thermalevaporation (VTE) deposition, sputter deposition, e-beam evaporation andchemical vapor deposition (CVD), or other similar techniques known inthe art. For example, the patterning of the plurality of bus lines mayinclude deposition by VTE through the shadow mask. As discussed furtherbelow, such patterning may result in a desirable profile of the buslines without, for example, further patterning steps. That is, a finalprofile shape of the bus lines may substantially correspond, or directlycorrespond, to a profile shape of the bus lines as they were depositedin S410.

It is noted that FIG. 4 depicts a manufacturing process where the firstelectrode is deposited before the bus lines. In an alternative process,the bus lines may be deposited before the first electrode, e.g. the buslines may be deposited on a substrate and the first electrode formed onthe bus lines and substrate. Such methods may be beneficial, forexample, in providing a flat interface, without bus lines, between afirst electrode layer and an organic stack formed over the firstelectrode layer. The method may continue with optional step S412.

In S412 a surface treatment, or other process, may be applied to form aninsulating layer over the bus lines deposited in S410. The insulatinglayer can provide insulation between the metal bus lines and the organiclayers to further prevent shorting. The insulating layer can alsoprevent charge injection from the metal bus lines into the organiclayers. In embodiments, such insulating layers, when present, may have arelatively thin profile compared to those formed in conventionaltechniques owing, for example, to the improved performance of thegradually sloped bus lines. An example of forming an insulating layer inS412 may include exposing an Al bus line surface to oxygen to form analuminum oxide layer. A further example may include VTE depositionthrough a shadow mask of insulating material such as SiO₂ or SiN overthe bus lines. The thickness of the insulating materials may be, forexample, <1000 Å. In embodiments, such steps may be performed withoutbreaking vacuum, which may help increase throughput and/or improvedevice lifetime. In embodiments, the final profile shape of theinsulating layer may correspond to a profile shape of the insulatinglayer as deposited. The method may continue with S420.

In S420, one or more organic layers, e.g. an organic layer stack, may begrown over, and/or on, the bus lines and first electrode, or, if aninsulating layer was formed in optional S412, the organic layer(s) maybe grown over, and/or on, the insulating layer and first electrode. Theorganic layer may be deposited through a third shadow mask, or via othertechniques known in the art. The method may continue with S430.

In S430, a second electrode may be deposited over the organic layer. Thesecond electrode may be a cathode. In other embodiments, the secondelectrode may be an anode. The second electrode may be formed, forexample, using a fourth shadow mask. Accordingly, and as describedfurther herein, an OLED stack including at least a first electrode, aplurality of bus lines, an organic layer and a second electrode may bemanufactured without any wet processing steps. FIG. 4 shows a processflow wherein the first electrode is deposited before the organic layersand before the second electrode. In an alternative embodiment, thesecond electrode is deposited before the organic layers and before thefirst electrode, wherein the bus lines are in electrical contact withthe first electrode. In an alternative embodiment, separate bus linesare in electrical contact with both the first and second electrodes.Aspects of an exemplary bus line profile are shown in FIG. 5.

As shown in FIG. 5, a bus line 510 deposited over an a first electrode500 according to aspects of the invention may include a relativelygradual slope, without sharp corners. In the embodiment shown in FIG. 5,an organic layer 520 is disposed on the bus line 510, and a secondelectrode 530 is disposed over the organic layer 520. The bus line 510may be an evaporated metal. Additional details of exemplary bus line 510are shown in FIG. 6.

A slope angle Θ of a sidewall of the bus line 510 may preferably be in arange of, for example, 0.01°-30°. The slope angle Θ may represent anangle that is measured based on a line L between two points on the busline sidewall at 10% and 90% respectively of bus line thickness T. Inembodiments, the maximum absolute value of the second derivative of thesidewall of the bus line layer with respect to distance along thesubstrate surface may be, for example, <1.0.

It should be noted that organic layer 520 may be deposited directly onthe bus line 510, or, optionally, there may be an insulating layerformed between the organic layer and the bus line. Alternativearrangements, such as the relative positions of the electrodes withrespect to the bus lines, are also possible depending, for example, onthe desired operation of the device.

The profiles shown in FIGS. 5 and 6 may be contrasted with a related artdevice as shown in FIG. 7. As shown in FIG. 7, a device including metalbus lines 710 over an ITO 700 may be formed by techniques includinglithography steps to pattern the metal bus lines 710. At least partlybecause of the sharp corners and/or relatively steep angle of thesidewalls, which induce strong local electric fields and can potentiallycause electrical shorting, a passivation (insulating) layer 720 isrequired on such devices to avoid short circuits between the bus lines710 and the OLED cathode (not shown).

A 3D atomic force microscope (AFM) image of the sidewall of an exemplarybus line formed by the inventors by VTE is shown in FIG. 8. Detaileddata in FIG. 9 shows that the root-mean-square (RMS) roughness value ofthe slope is around 11 nm, and the black cursor measures the height ofthe small peak to be about 31 nm. In embodiments, an RMS surfaceroughness of the bus line layer along the sidewall may be, for example,approximately, 30 nm or less. Bus lines deposited in this manner mayalso prove more secure against electrical shorting, compared to otherbus lines discussed further herein, owing to a gradual sidewall profile,smooth surface and reduced number of defects.

Such bus line features may allow for OLED devices to be formed by simplygrowing the OLED structure over the bus lines without a furtherinsulating layer, or with a relatively thin and/or low-resistivityinsulating layer compared to known devices. For example, the insulatinglayer may be required only to prevent charge injection from the buslines, rather than to prevent electrical shorting.

Returning to FIG. 4, it has been demonstrated by the inventors that theforegoing processes may be performed as an all-vacuum process that couldbe used to fabricate an OLED light panel. For example, an anode (such asITO or IZO) may be sputtered through a shadow mask. Then bus lines maybe disposed onto the anode as described herein. The organic layers maythen be deposited, for example, by VTE through a shadow mask, followedby the cathode through a separate shadow mask. Finally, thin filmencapsulation could also be applied in vacuum. Alternatively, asubstrate with an electrode and bus lines and optional insulating layercould be fabricated completely in vacuum (e.g. steps S400-S410 or S412in FIG. 4), and this could then be used to fabricate an OLED lightingpanel using any available means.

The inventors have further noted that the gradual sidewall profile ofmetal bus lines deposited through a shadow mask is benefited from afeathering effect during vapor deposition. Owing to a small gap betweenthe mask 810 and the substrate 820, as illustrated in FIG. 10A, whichmay be caused due to thermal expansion, rotation or weight of the mask,additional materials may be deposited onto the substrate beyond the maskopening. For example, if the gap is 100 μm, and the angle between theedge of mask opening with respect to the center of source material is10°, additional material will be deposited about 500 μm beyond the maskopening. If the target thickness of the material is 200 nm, very mildslope of the sidewall may be formed with an angle of only 0.02°.Alternatively, if the gap is less than 100 μm, less material may bedeposited beyond the mask opening and therefore a steeper slope may beexpected. The gap between the mask and substrate is dependent on factorssuch as mask thickness, mask material, substrate material, depositiontemperature etc.

In addition, the inventors have found that the sidewall profile of theVTE deposited bus lines (or other layers) may be controlled by properlypositioning the source material in combination with certain maskthickness, as can be seen in FIGS. 10A-10C. For example, a sharperprofile of VTE deposited bus line 800A is illustrated in FIG. 10A, wherethe source material 802 is positioned at the center, and the bus line800A is deposited through shadow mask 810 onto a substrate 820. The topportions of FIGS. 10A-10C provide an unobstructed view of the bus lineas deposited for clarity.

If the source 802 is positioned at an angle away from the center, theprofile may be altered to look like that in FIG. 10B, with a slope atboth edges. FIG. 10B shows the source material 802 in differentpositions. This is for illustration purposes only. In a manufacturingenvironment, relative changes in deposition angle would most likely beachieved by rotating the substrate, while the source material remainsfixed.

If the thickness of the mask 810 increases as shown in FIG. 10C, a moregradual transition of the bus line 800C can be achieved. Accordingly,the patterning of the plurality of bus lines may include at least one of(a) selecting a thickness of the shadow mask, (b) selecting a positionof a material source with respect to the shadow mask and (c) controllingthe gap between the shadow mask and the substrate based on the desiredfinal profile shape of the bus lines. In this regard, the inventors havefound that a thickness of the shadow mask may preferably be in a rangeof approximately 20 microns to 500 microns.

As further shown in FIG. 11, the angle Θ between the line 850 connectingsource and center of the substrate 820 and the normal line 860 of thesubstrate may be preferably in a range of approximately 0° to 20°.

The inventors have produced SEM images of VTE patterned bus line, wherevery gradual sidewall profile and edge transitions are clearly observed.FIG. 12 is an SEM images of (a) top view and (b) side view of a 2600 Åaluminum bus line deposited by VTE through a shadow mask. FIG. 13A showsan exemplary profile of a tested VTE metal bus line. The extracted slopeangle for Curve 2 is approximately 0.05°. The transition rates at PointsA and B on this curve also determine the smoothness of the sidewallprofile at the edge transition. Mathematically, the rate of change ofgradient, i.e. how smooth the transition is at the top and bottom of thebus line, can be acquired by calculating the second derivative of thecurve with respect to distance along the substrate surface at theselocations. For the purpose of extracting second derivative of points Aand B, the profile curve is first smoothed to eliminate local profilevariation caused by asperities. The second derivative of the smoothedcurve was then calculated. The maximum absolute value of the secondderivative of Curve 2 plotted in FIG. 13B is about 0.06, which is about40 times smaller than that of a curve derived from a conventionalprocessing technique, discussed further below. Accordingly, inembodiments, the maximum absolute value of the second derivative at bothedges (points A and B) of the bus line layer may be, for example, lessthan 1.0, less than 0.5, less than 0.1, etc.

It should also be noted that various patterns for the bus lines arepossible, including, for example, a branch-shaped pattern as shown inFIG. 14. An exemplary device was constructed with a similarbranch-shaped structure of metal bus lines, as shown in FIG. 14, made of2600 Å aluminum. A completed 15 cm×15 cm OLED light panel was shown toprovide uniform light output using such a structure, and, importantly,after extended operation, the OLED light panel did not develop anyelectrical shorts.

An organic light emitting device is also provided including features asdescribed herein. The device may include an anode, a cathode, and anorganic emissive layer disposed between the anode and the cathode. Theorganic emissive layer may include a host and a phosphorescent dopant,exemplary materials of which are discussed further below, following thecomparative test results.

Comparative Test Results

To compare the present subject matter to more conventional approaches,the inventors fabricated a large-area white OLED light panel usinglift-off processed metal bus lines. In this example, an insulating layerwas not included. A panel structure similar to that illustrated in FIG.3 was constructed. The organic material was in direct contact withelectrode and bus lines. The layout of the panel comprised nine stripes,and the anode of each OLED stripe was connected to metal bus lines, asshown in FIG. 3. The bus lines were patterned using photo lithography,where 6000 Å gold was e-beam evaporated, followed by a lift-off process.The OLED included, in order, an anode (1200 Å thick ITO), a holeinjection layer (100 Å thick LG101, available from LG Chemicals ofKorea), a hole transport layer (3800 Å thick NPD), a first emissivelayer (200 Å thick Host B doped with 24% Green Dopant A and 0.6% RedDopant A), a second emissive layer (75 Å thick Blue Host A doped with20% Blue Dopant A), a blocking layer (50 Å thick Blue Host A), a layer(450 Å thick layer of LG201, available from LG Chemicals of Korea and40% LiQ), and a cathode (10 Å thick layer of LiQ (lithium quinolate) anda 1000 Å thick layer of Al).

The inventors found that the panel lit up initially, however, a shortcircuit developed very soon on one of the bus lines. See FIGS. 21A and21B for cathode side, and anode side views, respectively. This singleshort resulted in the failure of the whole panel.

Further analysis showed that metal bus lines formed through a lift-offprocess have a sharp sidewall profile. FIG. 15 shows scanning electronmicroscope (SEM) images (taken from above and to the side) of 6000 Ågold bus lines deposited on an ITO anode. An SEM image of a side view ofthe metal layer is shown in FIG. 16. The slope of the sidewall was foundto be on average approximately 45-47°. The sharp corners at top and baseof the sidewalls will induce strong local electrical fields that canpotentially cause an electrical short. In addition, the organic layershave total thickness typically in the range of a few hundred nm, and itis hard to uniformly coat such thin layers of material over a tall andsteep sidewall. This will also result in a strong local electrical fieldwhere the bus line has the thinnest coverage which can potentially causean electrical short. Electrical shorting is also likely at places wherethe organic layer fails to cover the bus lines.

In addition to the abrupt transition at the bus line edge, asperities onthe metal side walls are also as large as hundreds of nanometers, asseen in FIG. 17. These sharp peaks can also serve as potential shortingpaths. Finally, particulate defects introduced by photolithography andlift-off may also cause electrical shorts. One such defect is shown inFIG. 17. In order to prevent shorting, a subsequent protectiveinsulating layer (e.g. polyimide or SiO₂) is normally required to coverthe bus line.

The area required for the overlap of the insulating layer covers part ofthe emissive area and decreases the fill factor of the OLED light panel,as illustrated in FIG. 18. Moreover, wet processes are involved in thelift-off method, such as developing and dissolving. Polymer insulatorscan easily absorb moisture during process (or even after process, duringsubstrate storage) and thus water may be retained in the device,reducing shelf life time. Also, photolithography and lift-off processesgenerate defects more easily, which may cause catastrophic failure ofthe device. Finally, photolithography and lift-off are time consumingand expensive processes.

The bus line profile from a lift-off process can be modified by usingdifferent photoresist, and adjusting exposure time etc. FIG. 19 showsscanning electron microscope (SEM) images of (a) top view and (b) sideview of a metal bus line profile fabricated from a modifiedphotolithography process. A bus line sidewall profile deposited andpatterned in a modified manner including a lift-off process is plottedin FIG. 20A. The angle of the slope extracted from this Curve 1 isreduced to about 33°. Using a modified lift-off process, the slope angleof the sidewall profile is less than 47° achieved using a conventionallift-off process in FIG. 16. However, this slope of the sidewall isstill steep enough to cause strong localized electric fields andpotentially an electrical short. The extracted maximum absolute value ofthe second derivative of Curve 1 is about 2.375, as shown in FIG. 20B.Thus, comparing the results shown in FIGS. 20A and 20B to those of theexemplary embodiments previously discussed with respect to FIGS. 13A and13B, it can be seen that bus lines deposited by VTE through a shadowmask can result in transitions that are orders of magnitude smootherthan lift-off processed bus lines.

Benefits of metal bus lines with a relatively smooth profile mayinclude: 1) less shorting owing to the smooth sidewall transition, 2)larger emissive area owing to the elimination of the insulating layerwhich enables higher efficiency and longer operational life time for aconstant light output, 3) longer shelf life time owing to theelimination of the insulating layer, such that water is no longer storedwithin the device 4) less shorting or visual defect owing to fewerparticles from fewer handling steps, and/or 5) lower cost owing toreduced/eliminated photolithography processes. Although specificembodiments discussed herein have used, for example, vacuum thermalevaporation (VTE) to pattern the bus lines, other vapor depositionsystem may include sputter deposition, e-beam evaporation and chemicalvapor deposition (CVD).

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but not limit to: aphthalocyanine or porphryin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

k is an integer from 1 to 20; X¹ to X⁸ is CH or N; Ar¹ has the samegroup defined above.

Examples of metal complexes used in HIL or HTL include, but not limit tothe following general formula:

M is a metal, having an atomic weight greater than 40; (Y¹-Y²) is abindentate ligand, Y¹ and Y² are independently selected from C, N, O, P,and S; L is an ancillary ligand; m is an integer value from 1 to themaximum number of ligands that may be attached to the metal; and m+n isthe maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹-Y²) is a 2-phenylpyridine derivative.

In another aspect, (Y¹-Y²) is a carbene ligand.

In another aspect, M is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidationpotential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

M is a metal; (Y³-Y⁴) is a bindentate ligand, Y³ and Y⁴ areindependently selected from C, N, O, P, and S; L is an ancillary ligand;m is an integer value from 1 to the maximum number of ligands that maybe attached to the metal; and m+n is the maximum number of ligands thatmay be attached to the metal.

In one aspect, the metal complexes are:

(O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, M is selected from Ir and Pt.

In a further aspect, (Y³—Y⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; groupconsisting aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and group consisting 2 to 10 cyclic structural units which are groups ofthe same type or different types selected from the aromatic hydrocarboncyclic group and the aromatic heterocyclic group and are bonded to eachother directly or via at least one of oxygen atom, nitrogen atom, sulfuratom, silicon atom, phosphorus atom, boron atom, chain structural unitand the aliphatic cyclic group. Wherein each group is furthersubstituted by a substituent selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

R¹ to R⁷ is independently selected from the group consisting ofhydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl,heteroalkyl, aryl and heteroaryl, when it is aryl or heteroaryl, it hasthe similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from CH or N.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule used ashost described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

k is an integer from 0 to 20; L is an ancillary ligand, m is an integerfrom 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

R¹ is selected from the group consisting of hydrogen, alkyl, alkoxy,amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl,when it is aryl or heteroaryl, it has the similar definition as Ar'smentioned above.

Ar¹ to Ar³ has the similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from CH or N.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atomsO, N or N,N; L is an ancillary ligand; m is an integer value from 1 tothe maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table XXXbelow. Table XXX lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

TABLE XXX MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injectionmaterials Phthalocyanine and porphryin compounds

Appl. Phys. Lett. 69, 2160 (1996) Starburst triarylamines

J. Lumin. 72-74, 985 (1997) CF_(x) Fluoro- hydrocarbon polymer

Appl. Phys. Lett. 78, 673 (2001) Conducting polymers (e.g., PEDOT:PSS,polyaniline, poly- pthiophene)

Synth. Met. 87, 171 (1997) WO2007002683 Phosphonic acid and sliane SAMs

US20030162053 Triarylamine or polythiophene polymers with conductivitydopants

EP1725079A1

Arylamines complexed with metal oxides such as molybdenum and tungstenoxides

SID Symposium Digest, 37, 923 (2006) WO2009018009 p-type semi-conducting organic complexes

US20020158242 Metal organo- metallic complexes

US20060240279 Cross- linkable compounds

US20080220265 Hole transporting materials Triarylamines (e.g., TPD,α-NPD)

Appl. Phys. Lett. 51, 913 (1987)

U.S. Pat. No. 5,061,569

EP650955

J. Mater. Chem. 3, 319 (1993)

Appl. Phys. Lett. 90, 183503 (2007)

Appl. Phys. Lett. 90, 183503 (2007) Triaylamine on spirofluorene core

Synth. Met. 91, 209 (1997) Arylamine carbazole compounds

Adv. Mater. 6, 677 (1994), US20080124572 Triarylamine with (di)benzo-thiophene/ (di)benzo- furan

US20070278938, US20080106190 Indolo- carbazoles

Synth. Met. 111, 421 (2000) Isoindole compounds

Chem. Mater. 15, 3148 (2003) Metal carbene complexes

US20080018221 Phosphorescent OLED host materials Red hosts Aryl-carbazoles

Appl. Phys. Lett. 78, 1622 (2001) Metal 8-hydroxy- quinolates (e.g.,Alq₃, BAlq)

Nature 395, 151 (1998)

US20060202194

WO2005014551

WO2006072002 Metal phenoxy- benzo- thiazole compounds

Appl. Phys. Lett. 90, 123509 (2007) Conjugated oligomers and polymers(e.g., polyfluorene)

Org. Electron. 1, 15 (2000) Aromatic fused rings

WO2009066779, WO2009066778, WO2009063833, US20090045731, US20090045730,WO2009008311, US20090008605, US20090009065 Zinc complexes

WO2009062578 Green hosts Aryl- carbazoles

Appl. Phys. Lett. 78, 1622 (2001)

US20030175553

WO2001039234 Aryltri- phenylene compounds

US20060280965

US20060280965

WO2009021126 Donor acceptor type molecules

WO2008056746 Aza- carbazole/ DBT/DBF

JP2008074939 Polymers (e.g., PVK)

Appl. Phys. Lett. 77, 2280 (2000) Spirofluorene compounds

WO2004093207 Metal phenoxy- benzooxazole compounds

WO2005089025

WO2006132173

JP200511610 Spirofluorene- carbazole compounds

JP2007254297

JP2007254297 Indolo- cabazoles

WO2007063796

WO2007063754 5-member ring electron deficient heterocycles (e.g.,triazole, oxadiazole)

J. Appl. Phys. 90, 5048 (2001)

WO2004107822 Tetra- phenylene complexes

US20050112407 Metal phenoxy- pyridine compounds

WO2005030900 Metal coordination complexes (e.g., Zn, Al withN{circumflex over ( )}N ligands)

US20040137268, US20040137267 Blue hosts Aryl- carbazoles

Appl. Phys. Lett, 82, 2422 (2003)

US20070190359 Dibenzo- thiophene/ Dibenzo- furan- carbazole compounds

WO2006114966, US20090167162

US20090167162

WO2009086028

US20090030202, US20090017330 Silicon aryl compounds

US20050238919

WO2009003898 Silicon/ Germanium aryl compounds

EP2034538A Aryl benzoyl ester

WO2006100298 High triplet metal organo- metallic complex

U.S. Pat. No. 7,154,114 Phosphorescent dopants Red dopants Heavy metalporphyrins (e.g., PtOEP)

Nature 395, 151 (1998) Iridium(III) organo- metallic complexes

Appl. Phys. Lett. 78, 1622 (2001)

US2006835469

US2006835469

US20060202194

US20060202194

US20070087321

US20070087321

Adv. Mater. 19, 739 (2007)

WO2009100991

WO2008101842 Platinum(II) organo- metallic complexes

WO2003040257 Osminum(III) complexes

Chem. Mater. 17, 3532 (2005) Ruthenium(II) complexes

Adv. Mater. 17, 1059 (2005) Rhenium (I), (II), and (III) complexes

US20050244673 Green dopants Iridium(III) organo- metallic complexes

Inorg. Chem. 40, 1704 (2001) and its derivatives

US20020034656

U.S. Pat. No. 7,332,232

US20090108737

US20090039776

U.S. Pat. No. 6,921,915

U.S. Pat. No. 6,687,266

Chem. Mater. 16, 2480 (2004)

US20070190359

US20060008670 JP2007123392

Adv. Mater. 16, 2003 (2004)

Angew. Chem. Int. Ed. 2006, 45, 7800

WO2009050290

US20090165846

US20080015355 Monomer for polymeric metal organo- metallic compounds

U.S. Pat. No. 7,250,226, U.S. Pat. No. 7,396,598 Pt(II) organo- metalliccomplexes, including poly- dentated ligands

Appl. Phys. Lett. 86, 153505 (2005)

Appl. Phys. Lett. 86, 153505 (2005)

Chem. Lett. 34, 592 (2005)

WO2002015645

US20060263635 Cu complexes

WO2009000673 Gold complexes

Chem. Commun. 2906 (2005) Rhenium(III) complexes

Inorg. Chem. 42, 1248 (2003) Deuterated organo- metallic complexes

US20030138657 Organo- metallic complexes with two or more metal centers

US20030152802

U.S. Pat. No. 7,090,928 Blue dopants Iridium(III) organo- metalliccomplexes

WO2002002714

WO2006009024

US20060251923

U.S. Pat. No. 7,393,599, WO2006056418, US20050260441, WO2005019373

U.S. Pat. No. 7,534,505

U.S. Pat. No. 7,445,855

US20070190359, US20080297033

U.S. Pat. No. 7,338,722

US20020134984

Angew. Chem. Int. Ed. 47, 1 (2008)

Chem. Mater. 18, 5119 (2006)

Inorg. Chem. 46, 4308 (2007)

WO2005123873

WO2005123873

WO2007004380

WO2006082742 Osmium(II) complexes

U.S. Pat. No. 7,279,704

Organometallics 23, 3745 (2004) Gold complexes

Appl. Phys. Lett. 74, 1361 (1999) Platinum(II) complexes

WO2006098120, WO2006103874 Exciton/hole blocking layer materialsBathocuprine compounds (e.g., BCP, BPhen)

Appl. Phys. Lett. 75, 4 (1999)

Appl. Phys. Lett. 79, 449 (2001) Metal 8-hydroxy- quinolates (e.g.,BAlq)

Appl. Phys. Lett. 81, 162 (2002) 5-member ring electron deficientheterocycles such as triazole, oxadiazole, imidazole, benzo- imidazole

Appl. Phys. Lett. 81, 162 (2002) Triphenylene compounds

US20050025993 Fluorinated aromatic compounds

Appl. Phys. Lett. 79, 156 (2001) Pheno- thiazine- S-oxide

WO2008132085 Electron transporting materials Anthracene- benzo-imidazole compounds

WO2003060956

US20090179554 Aza triphenylene derivatives

US20090115316 Anthracene- benzothiazole compounds

Appl. Phys. Lett. 89, 063504 (2006) Metal 8-hydroxy- quinolates (e.g.,Alq₃, Zrq₄)

Appl. Phys. Lett. 51, 913 (1987) U.S. Pat. No. 7,230,107 Metal hydroxy-beno- quinolates

Chem. Lett. 5, 905 (1993) Bathocuprine compounds such as BCP, BPhen, etc

Appl. Phys. Lett. 91, 263503 (2007)

Appl. Phys. Lett. 79, 449 (2001) 5-member ring electron deficientheterocycles (e.g., triazole, oxadiazole, imidazole, benzo- imidazole)

Appl. Phys. Lett. 74, 865 (1999)

Appl. Phys. Lett. 55, 1489 (1989)

Jpn. J. Apply. Phys. 32, L917 (1993) Silole compounds

Org. Electron. 4, 113 (2003) Arylborane compounds

J. Am. Chem. Soc. 120, 9714 (1998) Fluorinated aromatic compounds

J. Am. Chem. Soc. 22, 1832 (2000) Fullerene (e.g., C60)

US20090101870 Triazine complexes

US20040036077 Zn (N{circumflex over ( )}N) complexes

U.S. Pat. No. 6,528,187

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore includes variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

The invention claimed is:
 1. A method of manufacturing a light emittingpanel with a plurality of bus lines, the method comprising: forming afirst electrode layer; forming an organic layer stack over the firstelectrode layer; forming a second electrode layer over the organic layerstack; and patterning a plurality of bus lines by vapor depositionthrough a shadow mask, wherein, the plurality of bus lines are formed inelectrical contact with at least one of the first electrode layer andthe second electrode layer, and a final profile shape of the bus linescorresponds to a profile shape of the bus lines as deposited.
 2. Themethod of claim 1, wherein the plurality of bus lines are in electricalcontact with the first electrode layer and the first electrode layer isdeposited before the plurality of bus lines.
 3. The method of claim 1,wherein the plurality of bus lines are in electrical contact with thefirst electrode layer and the plurality of bus lines are depositedbefore the first electrode layer.
 4. The method of claim 1, wherein thepatterning of the plurality of bus lines includes at least one of vacuumthermal evaporation (VTE) deposition, sputter deposition, e-beamevaporation and chemical vapor deposition (CVD).
 5. The method of claim1, wherein the patterning of the plurality of bus lines includesdeposition by VTE through the shadow mask.
 6. The method of claim 5,wherein the patterning of the plurality of bus lines comprises at leastone of (a) selecting a thickness of the shadow mask, (b) selecting aposition of a material source with respect to the shadow mask and (c)controlling the gap between the substrate and the shadow mask based onthe desired final profile shape of the bus lines.
 7. The method of claim6, wherein the thickness of the shadow mask is in a range ofapproximately 20 microns to 500 microns.
 8. The method of claim 6,wherein the angle between the line connecting source and center of thesubstrate and the normal line of the substrate is in a range ofapproximately 0° to 20°.
 9. The method of claim 1, wherein the organiclayer stack is grown on the bus lines without an interceding insulator.10. The method of claim 1, further comprising forming an insulatorbetween the organic layer stack and the bus lines.
 11. The method ofclaim 10, wherein the insulator is formed without breaking a vacuumformed during the patterning of the bus lines by vapor deposition. 12.The method of claim 11, wherein the final profile shape of theinsulating layer corresponds to a profile shape of the insulating layeras deposited.
 13. The method of claim 1, wherein the forming of thefirst electrode layer, the forming of the organic layer stack, theforming of the second electrode layer and the patterning of the buslines are performed without wet processing.
 14. The method of claim 1,wherein a slope angle of a sidewall of the bus line is in a range of0.01°-30°, the slope angle measured based on a line between two pointson the bus line sidewall at 10% and 90% respectively of bus linethickness.
 15. The method of claim 14, wherein the maximum absolutevalue of the second derivative of the sidewall profile of the bus linelayer is <1.0.
 16. The method of claim 14, wherein a root-mean-square(RMS) of the surface roughness of the bus line layer along the sidewallis <30 nm.
 17. The method of claim 1, wherein the plurality of bus linesare in electrical contact with the second electrode layer and the secondelectrode layer is deposited before the plurality of bus lines.
 18. Themethod of claim 1, wherein the plurality of bus lines are in electricalcontact with the second electrode layer and the plurality of bus linesare deposited before the second electrode layer.
 19. The method of claim1, wherein a first set of the plurality of bus lines are in electricalcontact with the first electrode layer and a second set of the pluralityof bus lines are in electrical contact with the second electrode layer.